Section 1: Kinetic Theory
Section 2: Properties of Fluids
- How do ships float?
- Buoyancy: the ability of a fluid—a liquid or a gas—to exert an upward force on an object immersed in it.
- If the buoyant force is equal to the object’s weight, the object will float.
- An object will float if its density is less than the density of the fluid it is placed in.
- Pascal’s Principle
- Pressure: force exerted per unit area, or P=F/A.
- According to Pascal’s principle, pressure applied to a fluid is transmitted throughout the fluid.
- Hydraulic machines are machines that move heavy loads in accordance with Pascal’s principle.
Question: A barber raises his customer’s chair by applying a force of 150N to a hydraulic piston of area 0.01 m2. If the chair is attached to a piston of area 0.1 m2, how massive a customer can the chair raise? Assume the chair itself has a mass of 5 kg.
Answer: To solve this problem, first determine the force applied to the larger piston.

If the maximum force on the chair is 1500N, you can now determine the maximum mass which can be lifted by recognizing that the force that must be overcome to lift the customer is the force of gravity, therefore the applied force on the customer must equal the force of gravity on the customer.

If the chair has a mass of 5 kilograms, the maximum mass of a customer in the chair must be 148 kg.
- Bernoulli’s Principle
- According to Bernoulli’s principle, as the velocity of a fluid increases, the pressure exerted by the fluid decreases.
- Bernoulli’s principle was used in designing the hose end sprayer
- Fluid Flow
- Another property exhibited by fluid is its tendency to flow.
- Viscosity: The resistance to flow by a fluid
- When a container of liquid is tilted to allow flow to begin, the flowing particles will transfer energy to the particles that are stationary.
- If the flowing particles do not effectively pull the other particles into motion, then the liquid has a high viscosity, or a high resistance to flow. If the flowing particles pull the other particles into motion easily, then the liquid has low viscosity, or a low resistance to flow.
Section 3: Behavior of Gases
- Pressure
- Pressure is the amount of force exerted per unit of area.
- Pascal: the SI unit of pressure.
- Boyle’s Law
- If you squeeze gas into a smaller space, its particles will strike the walls more often—giving an increased pressure.
- If you give the gas particles more space, they will hit the walls less often—gas pressure will be reduced.
- According to Boyle’s law, if you decrease the volume of a container of gas and hold the temperature constant, the pressure of the gas will increase.
- As pressure is decreased the volume increases. As the pressure is increased, the volume will decrease.
- When Boyle’s law is applied to a real life situation, we find that the pressure multiplied by the volume is always equal to a constant if the temperature is constant.
- The Pressure-Temperature Relationship
- If the pressure becomes greater than the canister can hold, it will explode. At a constant volume, an increase in temperature results in an increase in pressure.
- Charles’s Law
- According to Charles’s law, the volume of a gas increases with increasing temperature, as long as pressure does not change.
- The volume of a gas shrinks with decreasing temperature
- Charles’s law can be explained using the kinetic theory of matter.
- As a gas is heated, its particles move faster and faster and its temperature increases.
- When using Charles’s law, the pressure must be kept constant.